Plant hormones

hormones control and coordinate growth and responses to light and gravity in plants

uses:
growth
seed germination
flowering
fruits, etc.

tropism:

• plant growth response when exposed to a stimulus

• positive - towards the stimulus

• negative - away from the stimulus

gravitropism:

• plants growth response to the earth’s gravitational field

• positive - plant roots towards gravitational attraction

• negative - plant stem away from gravitational attraction

• also known as geotropism

Phototropism:

• plant growth response to light

• positive - towards light → shoots/stem → max light for photosynthesis

• negative - away from light → root → less chance of drying up

Auxins

• change rate of elongation

• plant cells

• diffuse through plant

• made at the tips of the steam

• promotes growth in shoots

• root → inhibits growth

How Auxins enable phototropism

• sunlight breaks down auxins

• point towards sun has the lowest conc.

• shaded area has highest

• high conc. promotes growth

• negative and positive tropisms are inversely proportional